A range of topics in theoretical population genetics will be addressed, with an underlying theme of quantifying the behavior of genetic parameters under a variety of evolutionary processes and of determining the genetic basis of complex characters. The specific topics are: Gene conversion. The effects. of gene conversion, when acting in concert with mutation, recombination and drift, on measures of linkage disequilibrium will be quantified. This has implications for anomalous patterns of linkage disequilibrium being found in regions around human disease genes. Population structure. The best way of quantifying the genetic structure still appears to be with F-statistics or their analogues. Recent statistical theory suggests that analysis of variance on zero-one variables may lead to legitimate testing procedures. This will be explored. Related measures, suggested for populations with family structure, are very much related to the usual F-statistics, and this regression approach will be investigated -- especially in relation to the use of dominant markers. The possibility of using continuous data, instead of discrete population genetic data, will be considered. Locating QTLs. The growing density of genetic maps offers hope for being able to locate genes with major effects on quantitative traits. Consideration will be given to the effect on these procedures of the trait distributions being mixtures of (normal) distributions instead of single distributions. Descent measures. Descent measures have provided a language for expressing the behavior of many population and quantitative genetic parameters, but their evaluation is often very cumbersome. A related set of identity measures being used in a coalescent theory framework satisfy much simpler recursions. This coalescent approach will be carried to the wider set of descent measures as part of a unifying approach to population genetics.